Central Retinal Artery Occlusion

Aka: Central Retinal Artery Occlusion, CRAO, Branch Retinal Artery Occlusion, BRAO, Acute Retinal Ischemia

1. See Also
   1. Transient Ischemic Attack
   2. Acute Vision Loss
   3. Transient Monocular Blindness (Amaurosis Fugax)
   4. Central Retinal Vein Occlusion
2. Definitions
   1. Central Retinal Artery Occlusion (CRAO)
      1. Central Retinal artery is occluded affecting all Visual Fields
   2. Branch Retinal Artery Occlusion (BRAO)
      1. Branches of central Retinal artery are occluded, with segmental Vision Loss
3. Epidemiology
   1. Annual Incidence: One per 100,000 (U.S.)
   2. Age (mean): 60 years old
4. Pathophysiology
   1. Typically due to embolism to the Retinal artery
      1. May also occur due to thrombosis, inflammation or Eye Trauma
   2. Arteritis (e.g. Temporal Arteritis) accounts for <5% of cases
5. Risk Factors
   1. Age over 70 years
   2. Cardiovascular disease risks
      1. Coronary Artery Disease
      2. Diabetes Mellitus
      3. Hypertension
      4. Hyperlipidemia
      5. Hypercoagulable state
      6. Tobacco Abuse
   3. Migraine Headaches
   4. Collagen vascular disease (e.g. Systemic Lupus Erythematosus)
   5. Temporal Arteritis
   6. Sickle Cell Anemia
6. Causes: Ophthalmic artery Occlusion
   1. See Transient Ischemic Attack
   2. Cholesterol emboli
   3. Thrombotic emboli
   4. Vasculitis
   5. Hypoperfusion
      1. Hemodialysis
      2. Severe shock
      3. Nocturnal artery Hypotension (awake with Vision Loss)
         1. Associated with antihypertensives taken near bedtime
7. Symptoms
   1. See Transient Monocular Blindness (Amaurosis Fugax)
   2. Painless acute unilateral Vision Loss
      1. More than half of patients have only hand motion and light Perception
      2. CRAO causes Vision Loss over entire Visual Field, while BRAO results in focal Vision Loss
      3. May be preceded by prior episode of Amaurosis Fugax
   3. May be associated with other focal neurologic deficits
      1. See Transient Ischemic Attack
      2. Affects ipsilateral Carotid Artery circulation
8. Signs
   1. Visual Acuity severely reduced to light Perception only
      1. Branch Retinal Artery Occlusion may present with Visual Field cut
      2. Perform full Visual Field testing (differentiates CRAO from BRAO)
   2. Relative Afferent Pupillary Defect
      1. Pupil dilated with slow reaction
   3. Fundoscopic exam
      1. Retina appears pale-gray due to Retinal edema
      2. Macula with cherry-red spot on white-yellow background (collateral circulation from Choroid)
      3. Constricted arterioles
      4. Box-Carring of Retinal vessels
         1. Retinal vessels with interrupted columns of blood appear as train box cars
         2. Blood cells separate from serum
      5. Hollenhorst Plaques (white punctate Cholesterol emboli)
         1. "Glistening orange yellow flakes"
         2. Represent fragmented emboli at arteriole bifurcations
   4. Neck Exam
      1. Carotid Bruit
9. Exam
   1. See Eye Vital Signs
   2. Visual Fields and Visual Acuity testing drive management and prognosis
10. Differential Diagnosis
    1. See Acute Vision Loss
11. Labs
    1. Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (cRP)
       1. Increased in Temporal Arteritis
12. Diagnostics
    1. Electrocardiogram
       1. Evaluate for Atrial Fibrillation
13. Imaging: Obtain after acute stabilization (see management below)
    1. See Transient Ischemic Attack
    2. Evaluate as Transient Ischemic Attack or CVA (depending on deficits and timing)
       1. MRI Brain with Diffusion Weighted Imaging (CT misses "TIA" lesions) AND
       2. Evaluate Carotid Arteries: Carotid Ultrasound or Head and Neck CT Angiogram or MR Angiogram
    3. Echocardiogram
       1. Evaluate as performed in CVA and TIA
14. Precautions
    1. Central Retinal Artery Occlusion (CRAO) is a stroke of the eye
    2. Evaluate as Cerebrovascular Accident
15. Management
    1. Immediate, emergent Ophthalmology Consultation without delay
       1. Irreversible Vision Loss begins in the first 90-120 minutes
       2. Manage in similar fashion to a stroke protocol
    2. Lower Intraocular Pressure or dislodge Occlusion
       1. Lie patient supine with both Eyelids closed
       2. Ballot the eye: Apply intermittent pressure to eyeball
          1. Emergently perform as soon as possible
             1. Offers benefit within 6 hours (possibly up to 24 hours)
          2. Massage the globe with index fingers or each hand, then release suddenly
          3. Apply pressure in repeated cycles of 5-10 seconds on and 5 seconds off
          4. Perform for 20 cycles total or from 5-30 minutes
          5. Goal is to dislodge a thrombus
             1. Aqueous outflow increases with eye pressure
             2. Retinal perfusion increases with release of eye pressure
       3. Ocular Paracentesis
          1. Ophthalmologist aspirates 0.1 to 0.4 ml anterior chamber fluid via 27-30 gauge needle
          2. Goal to reduce Intraocular Pressure and shift the embolism distally
          3. May offer benefit up to 24 hours after onset
       4. Consider Hypercarbia
          1. Patient rebreathes into a paper bag for 10 minutes of each hour OR
          2. Inhalation of mix of 5% carbon dioxide and 95% oxygen
          3. Goal is to result in eye vessel vasodilation due to increased carbon dioxide concentrations
       5. Consider Aqueous Humor production strategies
          1. Mannitol 1 g/kg IV for 1 dose AND Acetazolamide 500 mg IV for 1 dose OR
          2. Acetazolamide 500 mg orally for 1 dose
       6. Consider hyperbaric oxygen
          1. Murphy-Lavole (2012) Undersea Hyperb Med 39(5): 943-53 +PMID: 23045923 [PubMed]
       7. Other measures that have been used (discuss with ophthalmology)
          1. Timolol maleate (0.5%) one drop topically
          2. Pilocarpine drops to eye
          3. Oral Nitroglycerin
          4. Pentoxifylline (Trental) three 600 mg tablets daily
          5. Laser arteriotomy
          6. Embolectomy
       8. Experimental or insufficient evidence to support
          1. Intraarterial Thrombolysis
             1. Page (2018) Front Neurol 9:76 [PubMed]
    3. Cerebrovascular Management
       1. Approach as Transient Ischemic Attack
       2. Evaluate patients age <50 years old for Hypercoagulable state causes (e.g. Antiphospholipid Antibody Syndrome)
    4. Temporal Arteritis (ESR or CRP meet criteria)
       1. Start empiric Corticosteroids
       2. Temporal artery biopsy or Doppler Ultrasound
16. Prognosis
    1. Vision Loss risk increases after 90 minutes (and esp. after 4 hours) of arterial Occlusion
    2. Spontaneous visual improvement may occur in first 7 days after onset
    3. Final Visual Acuity in affected eye <20/400
17. References
    1. Hartmann (2016) Crit Dec Emerg Med 30(6): 3-11
    2. Sales, Patel and Patel (2019) Crit Dec Emerg Med 33(12): 3-13
    3. Werner and St Peter in Herbert (2021) 21(9): 13-4
    4. Beatty (2000) J Accident Emerg Med 17:324-9 [PubMed]
    5. Biousse (2018) Ophthalmology 125:1597-607 [PubMed]
    6. Gelston (2020) Am Fam Physician 102(9):539-45 [PubMed]
    7. Pokhrel (2007) Am Fam Physician 76:829-36 [PubMed]